<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>FullScreenTest</title>
    <style>
    </style>
</head>
<body>
<div id="content" style="width:500px;height:500px;background:red;">
    这是被全屏的元素
    <button id='btn'>全屏</button>
    <button id="closeBtn">退出全屏</button>
</div>
<script>
function htmlTest(){
}
    let ele=document.getElementById("content");
    let loadContent;
    ele.onload=function(){
        loadContent="load complete"
    }

    function test(){
        backToEts.test("backToEts")
    }

    function fullScreen(el) {
        var rfs = el.requestFullScreen || el.webkitRequestFullScreen || el.mozRequestFullScreen || el.msRequestFullScreen,
            wscript;
        if(typeof rfs != "undefined" && rfs) {
            rfs.call(el);
            return;
        }
        if(typeof window.ActiveXObject != "undefined") {
            wscript = new ActiveXObject("WScript.Shell");
            if(wscript) {
                wscript.SendKeys("{F11}");
            }
        }
    }
    function exitFullScreen(el) {
        var el= document,
            cfs = el.cancelFullScreen || el.webkitCancelFullScreen || el.mozCancelFullScreen || el.exitFullScreen,
            wscript;
        if (typeof cfs != "undefined" && cfs) {
        cfs.call(el);
        return;
        }
        if (typeof window.ActiveXObject != "undefined") {
            wscript = new ActiveXObject("WScript.Shell");
            if (wscript != null) {
                wscript.SendKeys("{F11}");
            }
    }
    }

    var btn = document.getElementById('btn');
    var content = document.getElementById('content');
    btn.onclick = function(){
        fullScreen(content);
    }
    var closeBtn = document.getElementById('closeBtn');
    closeBtn.onclick = function(){
        exitFullScreen();
    }

    function elementFullScreen() {
        let content = document.getElementById('content');
        return content.requestFullscreen()
    }

    function elementExitFullScreen() {
        document.exitFullscreen()
    }

    function checkIsFullScreen() {
        var isFull =!! (document.webkitIsFullScreen || document.mozFullScreen || document.msFullscreenElement || document.fullscreenElement)
        return isFull
    }
    function getFontSize() {
        let fontSize = window.getComputedStyle(document.body, null).getPropertyValue('font-size')
        console.log(fontSize)
        return fontSize
    }
</script>
</body>
</html>